In the past, there has been little interest in the processing of heavy hydrocarbon oils and residua into useable liquid fuels. These heavy hydrocarbons include tar sand bitumen, oil sands and the residua left after higher quality petroleums have been distilled leaving a residue or as it is termed a residuum. In the recent past, various attempts have been made to upgrade these heavy hydrocarbon oils and residua in order to derive a new source for quality liquid fuels.
In U.S. Pat. No. 4,111,787, a process is set forth for the catalytic slurry hydroconversion of a heavy hydrocarbonaceous oil and coal mixture. The oil to be converted is admixed with an oil soluble metal compound which is converted to a catalyst in the presence of a hydrogen-containing atmosphere at elevated conditions. The reacted material is then mixed with coal in a subsequent hydroconversion zone for conversion of coal and oil to distillable oils. The use of a hydrogen donor solvent is specifically excluded.
U.S. Pat. No. 4,115,246 discloses a process for the upgrading of heavy liquid hydrocarbons in which a hydrogen donor diluent is mixed with the oil before being introduced into a cracker where the mixture is hydrocracked in the absence of hydrogen gas. The reaction product is fractionated and the residual pitch from the cracking reaction is partially oxidized to provide hydrogen for the rehydrogenation of depleted donor diluent to hydrogen donor diluent which is recycled to the front end of the process. The process is directed to the rehydrogenation of the donor solvent outside the cracking reactor.
U.S. Pat. No. 4,125,455 discloses a process for hydrotreating heavy residual oils with a catalyst comprising a Group 6B metal salt of a fatty acid. The heavy oil feedstock has a boiling point above 1,000.degree. F. The feedstock is admixed with the catalyst and is reacted with hydrogen under hydroconversion conditions to produce a tar residue and a lower boiling oil product. Hydrogen donor solvent is specifically excluded.
In U.S. Pat. No. 4,294,686, a process is disclosed for the upgrading of heavy hydrocarbon oils in which the oil is first atmospherically and vacuum distilled before being mixed with a hydrogen donor solvent and reacted under hydrocracking conditions to produce a lighter oil product. Catalyst and hydrogen gas are not utilized in the hydrocracking reactor. As a matter of fact, the use of a catalyst is taught to be ineffective for improving the hydrocracking reaction. However, the hydrogen donor solvent is catalytically rehydrogenated outside the cracking reactor prior to recycle to the front end of the process.
All of the above prior art attempts at upgrading heavy hydrocarbon oils and residua have failed to produce an optimum distillable oil product with minimal gaseous products. The present invention as set forth below utilizes a unique combination of process steps and conditions in order to maximize the distillable oil product, while minimizing the gaseous products, as well as solid residue of the hydroliquefaction reaction. In addition, the process of the present invention achieves increased denitrogenation of the hydrocarbon material.